1 files changed, 58 insertions, 0 deletions

diff --git a/fs/cifs/netmisc.c b/fs/cifs/netmisc.c
index ce87550e918f..992e80edc720 100644
--- a/fs/cifs/netmisc.c
+++ b/fs/cifs/netmisc.c
@@ -909,3 +909,61 @@ cifs_UnixTimeToNT(struct timespec t)
         /* Convert to 100ns intervals and then add the NTFS time offset. */
         return (u64) t.tv_sec * 10000000 + t.tv_nsec/100 + NTFS_TIME_OFFSET;
 }
+
+static int total_days_of_prev_months[] =
+{0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
+
+
+__le64 cnvrtDosCifsTm(__u16 date, __u16 time)
+{
+        return cpu_to_le64(cifs_UnixTimeToNT(cnvrtDosUnixTm(date, time)));
+}
+
+struct timespec cnvrtDosUnixTm(__u16 date, __u16 time)
+{
+        struct timespec ts;
+        int sec, min, days, month, year;
+        SMB_TIME * st = (SMB_TIME *)&time;
+        SMB_DATE * sd = (SMB_DATE *)&date;
+
+        cFYI(1,("date %d time %d",date, time));
+
+        sec = 2 * st->TwoSeconds;
+        min = st->Minutes;
+        if((sec > 59) || (min > 59))
+                cERROR(1,("illegal time min %d sec %d", min, sec));
+        sec += (min * 60);
+        sec += 60 * 60 * st->Hours;
+        if(st->Hours > 24)
+                cERROR(1,("illegal hours %d",st->Hours));
+        days = sd->Day;
+        month = sd->Month;
+        if((days > 31) || (month > 12))
+                cERROR(1,("illegal date, month %d day: %d", month, days));
+        month -= 1;
+        days += total_days_of_prev_months[month];
+        days += 3652; /* account for difference in days between 1980 and 1970 */
+        year = sd->Year;
+        days += year * 365;
+        days += (year/4); /* leap year */
+        /* generalized leap year calculation is more complex, ie no leap year
+        for years/100 except for years/400, but since the maximum number for DOS
+         year is 2**7, the last year is 1980+127, which means we need only
+         consider 2 special case years, ie the years 2000 and 2100, and only
+         adjust for the lack of leap year for the year 2100, as 2000 was a 
+         leap year (divisable by 400) */
+        if(year >= 120)  /* the year 2100 */
+                days = days - 1;  /* do not count leap year for the year 2100 */
+
+        /* adjust for leap year where we are still before leap day */
+        if(year != 120)
+                days -= ((year & 0x03) == 0) && (month < 2 ? 1 : 0);
+        sec += 24 * 60 * 60 * days; 
+
+        ts.tv_sec = sec;
+
+        /* cFYI(1,("sec after cnvrt dos to unix time %d",sec)); */
+
+        ts.tv_nsec = 0;
+        return ts;
+}